The abundance and isotope composition of the trace metal barium (Ba) allows us to track and quantify nutrient cycling throughout the Amazon Basin. In particular, we show that the Ba biological fingerprint evolves from that of a strong net nutrient uptake in the moutainous area of the Andes, towards efficient nutrient recycling in the plains of the Lower Amazon. Our study highlights the fact that the geochemical signature of rock-derived nutrients transported by the Amazon is scarred by Life.

This paper deals with the mathematical representation of concentration–discharge relationships. We propose a two-sided affine power scaling relationship (2S-APS) as an alternative to the classic one-sided power scaling relationship (commonly known as power law). We also discuss the identification of the parameters of the proposed relationship, using an appropriate numerical criterion, based on high-frequency chemical time series of the Orgeval-ORACLE observatory.

This Technical Note deals with the mathematical representation of concentration-discharge relationships and with the identification of its parameters. We propose a two-sided power transformation alternative to the classical log-log transformation, and a multicriterion identification procedure allowing determining parameters that are efficient, both from the concentration and the load points of view.

The grain-size distribution of ancient alluvial systems is commonly determined from sections of gravel deposits exposed vertically to reconstruct paleo-environments or changes in tectonics and/or climate. To test whether such a grain-size distribution is equivalent to one of the sediments that was in direct contact with the flow at the time of deposition, we dug a large trench in an active gravel-bedded, braided river. We show that the granulometry is uniform at the scale of the active layer.

As knowledge in biology and geology explodes, science becomes increasingly specialized. Given the overlap of the environmental sciences, however, the explosion in knowledge inevitably creates opportunities for interconnecting the biogeosciences. Here, 30 scientists emphasize the opportunities for biogeoscience collaborations across the world’s remarkable long-term environmental research networks that can advance science and engage larger scientific and public audiences.

Focusing on the usage of integrated models and in situ Earth observatory networks, three challenges are identified to advance understanding of ESD, in particular to strengthen links between biotic and abiotic, and above- and below-ground processes. We propose developing a model platform for interdisciplinary usage, to formalize current network infrastructure based on complementarities and operational synergies, and to extend the reanalysis concept to the ecosystem and critical zone.

Plants and soil microbiota play an active role in rock weathering. Here we show that the coupling between erosion and weathering might be established by nutrients that are taken up by trees, are not recycled from plant litter and are missing in the dissolved river flux due to forest re-growth after clear cutting or due to erosion as coarse woody debris. To track this nutrient pathway we used magnesium stable isotopes in combination with innovative metrics over annual and millennial timescales.

To be better prepared for drought, we need to be able to characterize how they begin, translate to on-ground impacts and how they end. We created a 100-year drought record for an area on the east coast of Australia and compared this with soil moisture and vegetation data. Drought reduces vegetation and soil moisture, but recovery rates are different across different catchments. Our methods can be universally applied and show the need to develop area-specific data to inform drought management.

Recharge assessment in the shared transboundary Western Aquifer Basin is highly relevant, scientifically as well as hydropolitically (in Israeli–Palestinian water negotiations). Our unique combination of field-measured soil characteristics and soil moisture time series with soil moisture saturation excess modelling provides a new basis for the spatial differentiation of formation-specific groundwater recharge (at any scale), applicable also in other previously ungauged basins around the world.

Secondary dryland salinity is a global land degradation issue. Our understanding of causal processes is adapted from wet and hydrologically connected landscapes and concludes that low end-of-catchment runoff indicates land clearing alters water balance in favour of increased infiltration and rising groundwater that bring salts to the surface causing salinity. This study shows surface flows play an important role in causing valley floor recharge and dryland salinity in low-gradient landscapes.

Soil moisture plays an important role in hydrological modelling. However, most existing in-situ observation networks rarely provide sufficient coverage to capture soil moisture variations. Clearly, there is a need to develop a systematic approach, so that with the minimal number of sensors the soil moisture information could be captured accurately. In this study, a simple and low-data requirement method is proposed, which can provide very efficient soil moisture estimations.

Most commercial automatic rain samplers are costly and do not prevent evaporation from the collection bottles. Hence, we have developed a microcontroller-based collector enabling timer-actuated integral rain sampling. The simple, low-cost device is robust and effectively minimizes post-sampling evaporation. The excellent performance of the collector during an evaporation experiment in a lab oven suggests that even multi-week field deployments in warm climates are feasible.

Measuring Earth's changing environment is a critical part of natural science, but to date most of the equipment to do so is expensive, proprietary, and difficult to customize. We addressed this challenge by developing and deploying the ALog, a low-power, lightweight, Arduino-compatible data logger. We present our hardware schematics and layouts, as well as our customizable code library that operates the ALog and helps users to link it to off-the-shelf sensors.

The research undertaken for this study has allowed for an accurate direct comparison of indigenous and introduced tree water use. The measurements of trees growing in the understorey indicate significant water use in the subcanopy layer. The results showed that individual tree water use is largely inter-species specific. The introduced species remain active during the dry winter periods, resulting in their cumulative water use being significantly greater than that of the indigenous species.

We demonstrate how thermal infrared images can be used for mapping the appearance and disappearance of water at the surface. The use of thermal infrared images allows for mapping this appearance and disappearance for various temporal and spatial resolutions, and the images can be understood intuitively. We explain the necessary steps in detail, from image acquisition to final processing, by relying on image examples and experience from an 18-month mapping campaign.

To evaluate the potential value of streamflow estimates for hydrological model calibration, we created synthetic streamflow datasets in various temporal resolutions based on the errors in streamflow estimates of 136 citizens. Our results show that streamflow estimates of untrained citizens are too inaccurate to be useful for model calibration. If, however, the errors can be reduced by training or filtering, the estimates become useful if also a sufficient number of estimates are available.

We analyze changes in catchment evaporation estimated from the water balances of 156 catchments in Austria over 1977–2014, as well as the possible causes of these changes. Our results show that catchment evaporation increased on average by 29 ± 14 mm yr−1 decade−1. We attribute this increase to changes in atmospheric demand (based on reference and pan evaporation), changes in vegetation (quantified by a satellite-based vegetation index), and changes in precipitation.

We have developed a new mobile automated water sampling device for environmental research and other applications where waters need to be tested for compliance with environmental/health regulations. It has two main advantages over similar devices: firstly, it injects water samples directly into airtight vials to prevent any change in sample properties through contamination, evaporation and gas exchange. Secondly, it can hold up to 160 sample vials, while other devices only hold up to 24 vials.

The study examined dynamics of DOC export from a permafrost peatland catchment located in northeastern China. The findings indicated that the DOC export is a transport-limited process and the DOC load was significant for the net carbon balance in the studied catchment. The flowpath shift process is key to observed DOC concentration, resources and chemical characteristics in discharge. Permafrost degradation would likely elevate the proportion of microbe-originated DOC in baseflow.

We investigate the usefulness of assimilating crowdsourced observations from a heterogeneous network of sensors for different scenarios of citizen involvement levels during the flood event occurred in the Bacchiglione catchment in May 2013. We achieve high model performance by integrating crowdsourced data, in particular from citizens motivated by their feeling of belonging to a community. Satisfactory model performance can still be obtained even for decreasing citizen involvement over time.

The internal variability of paleomeanders strongly influence water fluxes in alluvial plains. This study presents the results of a hydrogeophysical investigation that provide a very detailed characterization of the geometry of a wide paleomeander. The presented case study, situated in the Seine River basin (France), represents a common sedimentary and geomorphological structure in alluvial plains worldwide.

We use sap velocity measurements from 61 trees on 132 days to gain knowledge about the controls of landscape-scale transpiration, distinguishing tree-, stand- and site-specific controls on sap velocity and sap flow patterns and examining their dynamics during the vegetation period. Our results show that these patterns are not exclusively determined by tree characteristics. Thus, including site characteristics such as geology and aspect could be beneficial for modelling or management purposes.

We used a coupled hydrological–hydrochemical approach to assess the impact of snow on river and lake water chemistry across a permafrost gradient in very poorly studied Western Siberia Lowland (WSL), encompassing > 1.5 million km2. The riverine springtime fluxes of major and trace element in WSL rivers might be strongly overestimated due to previously unknown input from the snow deposition.

Humans have profoundly altered land cover and soil drainage for agricultural purposes in the Midwestern USA. Here we investigate whether climate alone can explain recent increases in observed streamflows throughout the region. Using multiple analyses, including statistical tests and water budgets, we conclude that historical drainage installation has likely amplified the streamflow response to regional precipitation increases. We stress that better documentation of artificial drainage is needed.

The investigation of groundwater-lake water interactions in a highly permeable boreal terrain using several indicators showed that lowland lakes are imbedded into the groundwater system and are thus relatively resilient to short-term hydroclimatic change while upland lakes rely more on precipitation as their main water input, making them more sensitive to evaporative drawdown. This suggest that landscape position controls the vulnerability of lake water levels to hydroclimatic change.

Monitoring water storage changes beyond the point scale is a challenge. Here, we show that an integrative and non-invasive way is by observing variations of gravity that are induced by water mass changes. A high-precision superconducting gravimeter is successfully operated in the field and allows for direct and continuous monitoring of the water balance and of its components, such as actual evapotranspiration.

We compare lysimeter and eddy covariance (EC) flux measurements of evapotranspiration at a research catchment in Switzerland. The measurements are compared on various timescales, and with respect to a 40-year long-term lysimeter time series. Overall, the lysimeter and EC measurements agree well, especially on the annual timescale. Furthermore, we identify that lack of reliable EC data during/after rainfall events significantly contributes to an underestimation of EC evapotranspiration.

We present a newly developed instrument package that enables the online analysis of stable water isotopes and major ion chemistry at 30 min intervals in the field. The resulting data streams provide an unprecedented view of hydrochemical dynamics on the catchment scale. Based on a detailed analysis of the variable behavior of isotopic and chemical tracers in stream water and precipitation over a 4-week period, we developed a conceptual hypothesis for runoff generation in the studied catchment.

We use historical records to extend current understanding of flood risk, examining past spatial and temporal variability and ask are the perceived high-magnitude flood events witnessed in recent years really unprecedented? We identify that there are statistically significant relationships between the British flood index and climatic drivers, whereby the largest floods often transcend single catchments affecting regions and that the current flood-rich period is not unprecedented.

Our long-term results are relevant to land areas that are in pasture and those that have reverted back to forests. We found that within a deciduous forest, species identity matters in terms of how much precipitation leaves the watershed as evapotranspiration versus water yield. We demonstrate that a shift in tree species composition from species with ring-porous xylem to species with diffuse-porous xylem can increase water use, and in turn, produce a long-term reduction in water yield.

The 2-year measurements of δ2H and δ18O in rainfall, stream, soil, and groundwater revealed that surface and groundwater are isotopically disconnected from the annual precipitation cycle but showed bidirectional interactions in the Schwingbach catchment. We established a hydrological model to estimate spatially distributed groundwater ages and flow directions. Our model revealed complex age dynamics and showed that runoff must have been stored in the catchment for much longer than event water.

In this study, we focused on analyzing the variation and factors influencing deep soil moisture content based on a soil moisture survey of the Ansai watershed. Our results revealed the variation characteristics of deep soil moisture and its controlling mechanism at a moderate scale. The results of this study are of practical significance for vegetation restoration strategies and the sustainability of restored ecosystems.

Laos and Vietnam have switched from net forest loss to net forest expansion between 1990 and 2015. Based on long-term field measurements of land use, river flows, and weather data, we demonstrate that forest expansion can have extreme, yet opposite, impacts on water resources, depending on how the newly established tree-based cover is managed. The conversion of annual crops to teak plantations in Laos or to naturally regrowing forests in Vietnam led to increased and decreased flows, respectively.

Cosmic-ray neutron sensors bridge the gap between point-scale measurements of soil moisture and remote sensing applications. We tested four distinct methods to calibrate the sensor in a temperate forest environment using different soil moisture weighting approaches. While the variable leaf biomass of the deciduous trees had no significant influence on the calibration, it proved necessary to modify the standard calibration method to achieve the best sensor performance.

Soil moisture estimates from a novel method were evaluated in two semiarid watersheds. We found good agreements between the technique and estimates derived from watershed instruments designed to close the water balance. We then investigated local hydrologic processes and link between evapotranspiration and soil moisture obtained from the novel measurements.

This paper illustrates the experimental and monitoring set-up of the 66 ha Hydrological Open Air Laboratory (HOAL) in Petzenkirchen, Lower Austria, which allows meaningful hypothesis testing. The HOAL catchment features a range of different runoff generation processes (surface runoff, springs, tile drains, wetlands), and is convenient from a logistic point of view as all instruments can be connected to the power grid and a high-speed glassfibre local area network.

The transit time of water is a key indicator of hydrological processes at the catchment scale. Our results suggest that the use of tritium time series in streamwater can be highly valuable for assessing the temporal variations in the transit time of older groundwater contributions to streamflow. We also show that, shortly after high flow events, the transit time of the old water fraction increases and tends to approach the groundwater residence time.

Isotope and hydrochemical tracers are tested providing new insights to isotope hydrograph in semi-arid areas in southern Africa. This study provides a spatial hydrochemical characterization of surface and groundwater sources, end member mixing analysis, and two- and three-component hydrograph separations. Results showed that the Kaap catchment is mainly dominated by groundwater sources, and direct runoff is positively correlated with the Antecedent Precipitation Index during the wet season.

This study documents the age of water that contributes to rivers in upper catchments using the radioactive tracer tritium. River water in the upper Ovens Valley (Australia) is several years to decades old and water from different parts of the catchment (e.g., soil, regolith, and groundwater) is mobilised at different flow conditions. The results indicate that these rivers are buffered against short term climate variability but are susceptible to longer-term climate and land use changes

A field method for assessing soil moisture in semi-arid conditions is proposed and tested in terms of inter-rater reliability with 40 Tanzanian farmers, students and experts. The seven wetness classes are based on qualitative indicators that one can see, feel or hear. It could be shown that the qualitative wetness classes reflect differences in volumetric water content and neither experience nor a certain level of education was a prerequisite to gain high agreement among raters.

River flows depend not only on how much water is in a catchment, but also on where the water is stored, which changes over time. We monitored streamflow, soil moisture, and groundwater levels in a NZ catchment, to find out what controls water storage and variability. We found that the catchment had a summer mode where water storage is controlled by near-surface interactions of water with soils and vegetation, and a winter mode where water storage is controlled by deeper groundwater movement.

Groundwater surface mapping is used as an independent data set to better estimate groundwater discharge to streamflow. The groundwater surfaces indicated when other techniques likely overestimated the groundwater discharge component of baseflow. Groundwater surfaces also identified areas where regional groundwater could not be contributing to tributary streamflow. This method adds significant value to water resource management where sufficient groundwater monitoring data are available.

This study follows organic carbon from soils along sediment flow paths at catchment scale to analyse the evolution of OC pools. Selectivity of particles during detachment and transport, and protection of OC during transport and deposition are key for the concentration and quality of OC at depositional settings and for the terrestrial carbon sink. OC can also be increased by ecological processes and by replacement in eroded areas, converting catchments into relevant sinks for C budget.

This paper presents measurements of the balance of water inputs and outputs over 1 year for a river basin in the Andes of Peru. Our results show that the annual water budget is balanced within a few percent uncertainty; that is to say, the amount of water entering the basin was the same as the amount leaving, providing important information for understanding the water cycle. We also show that seasonal storage of water is important in sustaining the flow of water during the dry season.

We present a new prototype lab in the field named River Lab (RL) designed for water quality monitoring to perform a complete analysis at sub-hourly frequency of major dissolved species in river water.
The article is an analytical paper to present the proof of concept, its performances and improvements. Our tests reveal a significant improvement of reproducibility compared to conventional analysis in the laboratory. First results are promising for understanding the critical zone.

We present a new prototype lab in the field named River Lab (RL) designed for water quality...